A Visual Encyclopedia of the Periodic Table

138

The Boron Group

Tl

81

Thallium was named after the Greek

word thallos, which means “green shoot”:

it was first identified from the colours in its

flame, which includes a bright green light.

Thallium was discovered in 1861 by William

Crookes and Claude-Auguste Lamy. Although

both chemists worked separately, they found

the element in the same way – as a residue while

making strong acids using the mineral pyrite.

Thallium was later found to exist in larger amounts

in other minerals, including thallium alum.

Pure thallium is toxic and has to be handled

Forms

Thallium

This soft and silver y metal is kept

in a sealed glass tube as it is highly

toxic and reacts easily with air.

This mineral contains

iron, sulfur, and tiny

amounts of thallium.

The grey crust on this aluminium mineral

contains small amounts of thallium.

Pyrite

Laboratory sample of pure thallium in an airless vial

81 81 123

State: Solid

Discovery: 1861

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